Sterilizing PLA for Medical Use – How PLA Survived Autoclaving

We determined the best candidate 3D printing material and infill geometry from this analysis, Essentium PLA Gray filament and “grid” infill, respectively, and printed standard surgical Army-Navy retractors to test the mechanical strength of PLA following annealing and autoclaving interventions, both independently and together. Standard and strength-optimized Army-Navy retractor designs created by Chen et al. in Autodesk® Fusion 360™ were used, obtained as STL files (Fig. 2a, b) [27]. The annealing intervention was submersion of the retractors in a 100 °C water-bath for 30 mins, and the autoclaving intervention was autoclaving the retractors for 45 mins at 134 °C and a pressure of 375 PSI.

Specified by Chen et al., the print settings for strength-optimized 3D printed PLA Army-Navy retractors were 30% infill, 3 perimeters, 0.25 in. thickness, 0.75 in. width, “triangles” infill geometry and reinforced joints, which optimizes retractor strength but does not aim to minimize deformation [27].

a Standard Army-Navy retractor and b strength-optimized Army-Navy retractor designs in inches created in AutoDesk® Fusion 360™ obtained from Chen et al. c Retractor orientation on the build plate to eliminate need for support material
a Standard retractors warping after hot water-bath annealing and b after autoclaving. c Strength-optimized retractor without intervention (right) and warping after hot water-bath annealing (left)

Standard retractors without intervention failed at 95 N +/− 2.4 N. Hot water-bath annealed retractors failed at 127.3 N +/− 10 N. Autoclave only retractors failed at 15.7 N +/− 1.4 N. Hot water-bath annealed then autoclaved retractors failed at 19.8 N +/− 3.1 N.

Strength-optimized retractors, after the annealing then autoclaving intervention, failed at 164.8N +/− 12.5 N (Fig. 5). For comparison, these retractions fail at 538.5 N +/− 24.9 N without intervention. Retractors displayed mild warping after hot water-bath annealing (Fig. 3).

Chen et al. “Identifying a commercially-available 3D printing process that minimizes model distortion after annealing and autoclaving and the effect of steam sterilization on mechanical  strength.” Date Accessed: April 25, 2020

This research will definitely assist me with designing future models.

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Sandra James

Blogger, Designer, and Astrologer

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